The invention relates to a method of exchanging data between a remote control unit and a current source of a welding unit, and to a remote control unit used in such a method.
An arc welding machine is knownxe2x80x94as disclosed in DE 29 04 458 A1xe2x80x94in which an adjustable power component for generating a welding current can be controlled via a control system. To this end, the power component is connected to an electrode holder and the workpiece by respective welding power cables and is equipped with an adjustment system co-operating with the control system which can be adjusted manually or by means of a remote control unit. The remote control unit is disposed between the workpiece and the electrode holder, in particular a welding torch, and has a manually operable device for adjusting the welding current. This remote control unit co-operates with a detection system in the control system of the welding unit. The current input of the remote control unit is adjusted via the remote control unit, whereby the power input can be increased. The change in current flowing to the remote control unit is detected by the detection system and the desired value for the welding current adjusted accordingly. The disadvantage of this system is that external influences can trigger changes in resistance in the control circuit, which can lead to an increase in no-load current and hence to an incorrect adjustment of the desired value for the welding device.
Another arc welding machine with an adjustable power component is knownxe2x80x94as disclosed in DE 33 29 216 A1xe2x80x94in which a remote control unit is used between the conducting surfaces of a workpiece and a welding electrode. Depending on the sequence of the conducting surfaces and the polarity of the workpiece and welding electrode, a higher or lower frequency of welding voltage is superimposed on the welding voltage. A control device in the welding unit increases or reduces the welding current until the control circuit or current circuit is closed via the power component. The disadvantage of this system is that the resetting procedure or setting procedure has to be repeated several times in order to run intermediate welding tests to ascertain whether the newly set desired value for the welding current corresponds to the desired value.
The underlying objective of the present invention is to propose a remote control unit, offering a simple way of setting the exact desired value of a welding parameter in a welding unit remotely.
This objective is achieved by the invention with a method of exchanging data between an external component consisting of a remote control unit having two inputs, and a current source of a welding unit, comprising the steps of carrying out a serial data exchange between the welding unit and the remote control unit, directly across welding lines constituting connecting lines to a welding torch and to a workpiece, on the basis of digital levels, carrying out a two-way data exchange between the current source of the welding unit and the external component consisting of the remote control unit, establishing a continuous current flow between the two inputs via a switching device of the remote control unit and forming the digital levels in such a way that when a switch component of the switching device is closed a total resistance value between the two inputs of the remote control unit is changed. The advantage of this system is that by using a serial data exchange in the form of a data protocol, a large amount of data can be transferred, which means that a large number of different welding parameters can be amended with only one remote control unit. Another advantage resides in the fact that because a two-way data exchange is operated, individual welding parameters, in particular their desired values for the welding unit or the current source, can be consulted and then shown on the display of the remote control unit, enabling the user to take a reading, and/or amended.
Other advantageous features are defined in claims 2 to 6. The advantages which they offer can be taken from the detailed description of the drawings.
The objective of the invention is also achieved with a remote control unit for a current source of a welding unit, the remote control unit comprising at least one setting unit and a current supply unit, and in order to activate the remote control unit it is placed in contact by means of a respective input with a workpiece and an electrode holder; a digitally programmable logic unit connected to a switching device which comprises at least one resistor and a switch component, in order to generate digitally sequential levels, the switch component being in turn connected to an input for the electrode holder and the workpiece, and another resistor is connected in parallel with the switch component to form a continuous current flow in the switching device. The resultant advantage is that the design of the remote control unit permits a serial data transmission, which means that any amount of data can be transferred. Another advantage is that it offers a simple way of selecting different welding parameters by activating a setting element on the remote control unit, so that when using the remote control unit the user has the option of amending the desired value for every welding parameter without having to enter a setting from the input and/or output device on the welding unit.
In one application of a remote control unit of this type, a two-way data exchange can advantageously be operated between the remote control unit and the welding unit, which means, for example, that if the user enters an incorrect setting, it can be detected by the control system of the welding unit and the user can be alerted to the fact by the control system, which transmits a corresponding data protocol to the user via the remote control unit.
Other advantageous embodiments are defined in claims 8 to 18. The advantages achieved as a result are explained in the detailed description of the drawings.